An internally consistent model for the thermodynamic properties of Fe?Mg-titanomagnetite-aluminate spinels

Sack, Richard O.; Ghiorso, Mark S.

doi:10.1007/bf00321989

Cited by 211 publications

(105 citation statements)

References 108 publications

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“…The results of experimental and theoretical studies [4,5,38,[43][44][45][46][47][48][49][50] allowed us to estimate the equilibration temperature and oxygen fugacity of coexisting magnetite and its exsolution products based on their chemical composition. Unfortunately, we can perform only a very approximate estimation of PT-conditions of Al-rich magnetite exsolutions based on the models of magnetite-spinel miscibility [5,45]; however, Fe-Ti oxide geothermobarometers are much more informative.…”

Section: Introductionmentioning

confidence: 99%

Subsolidus Evolution of the Magnetite-Spinel-UlvöSpinel Solid Solutions in the Kovdor Phoscorite-Carbonatite Complex, NW Russia

et al. 2017

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Abstract:The Kovdor phoscorite-carbonatite ore-pipe rocks form a natural series, where apatite and magnetite first gradually increase due to the presence of earlier crystallizing forsterite in the pipe marginal zone and then decrease as a result of carbonate development in the axial zone. In all lithologies, magnetite grains contain (oxy)exsolution inclusions of comparatively earlier ilmenite group minerals and/or later spinel, and their relationship reflects the concentric zonation of the pipe. The temperature and oxygen fugacity of titanomagnetite oxy-exsolution decreases in the natural rock sequence from about 500 • C to about 300 • C and from NNO + 1 to NNO − 3 (NNO is Ni-NiO oxygen fugacity buffer), with a secondary positive maximum for vein calcite carbonatite. Exsolution spinel forms spherical grains, octahedral crystals, six-beam and eight-beam skeletal crystals co-oriented with host magnetite. The ilmenite group minerals occur as lamellae oriented along {111} and {100} planes of oxy-exsolved magnetite. The kinetics of inclusion growth depends mainly on the diffusivity of cations in magnetite: their comparatively low diffusivities in phoscorite and carbonatites of the ore-pipe internal part cause size-independent growth of exsolution inclusions; while higher diffusivities of cations in surrounding rocks, marginal forsterite-rich phoscorite and vein calcite carbonatite result in size-dependent growth of inclusions.

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Section: Introductionmentioning

confidence: 99%

Subsolidus Evolution of the Magnetite-Spinel-UlvöSpinel Solid Solutions in the Kovdor Phoscorite-Carbonatite Complex, NW Russia

et al. 2017

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“…and Mg 2+ and Al 3+ in the spinel solid solution (Sack, 1982;Sack andGhiorso, 1991a, 1991b), and likely represent crystallization from a rapidly evolving and fractionating melt.…”

Section: +mentioning

confidence: 99%

“…Cr-spinel is a complex mineral solution best described by reciprocal solution theory (Wood and Nicholls, 1978;Sack, 1982;Sack andGhiorso, 1991a, 1991b). Spinel solution energetics must be accounted for if spinel compositions are to be used to infer coexisting melt composition.…”

Section: Chemistrymentioning

confidence: 99%

“…In view of its widespread occurrence, it is underused for exploring petrological phenomena. As an illustration, only a few studies of backarc basin Cr-spinel have been made (e.g., Dick and Bullen, 1984;Hawkins and Melchior, 1985;Forsythe and Fisk, this volume), even though the complex crystal chemistry of Crspinel provides a wealth of opportunities for its use as a petrogenetic indicator of both intensive and extensive variables (Irvine, 1965(Irvine, ,1967Fisk and Bence, 1980;Sack, 1982;Roeder and Reynolds, 1991;Sack andGhiorso, 1991a, 1991b). In particular, Cr-spinel is a highly sensitive indicator of mineral-melt equilibria and disequilibria, with recent studies using several approaches to determine pathways of magma evolution (Fisk and Bence, 1980;Natlandetal., 1983;Dick and Bullen, 1984;Allan et al, 1988;Natland, 1989;Roeder and Reynolds, 1991;Scowen et al, 1991;.…”

Section: Introductionmentioning

confidence: 99%

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Cr-Spinel in Depleted Basalts from the Lau Backarc Basin: Petrogenetic History from Mg-Fe Crystal-Liquid Exchange

Allan¹

1994

Proceedings of the Ocean Drilling Program

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Cr-spinels in cores drilled during Ocean Drilling Program Leg 135 exhibit wide variations in composition and morphology that reflect complex petrogenetic histories. These Cr-spinels are found within basaltic lava flows that erupted in north-trending sub-basins within the Lau Basin backarc. Cr-spinels from Sites 834 and 836 occur as euhedral groundmass grains and inclusions in Plagioclase, and range up to 300 µm in size. These Cr-spinels are similar in composition, morphology, and mode of occurrence to Cr-spinels found within depleted, N-type mid-ocean-ridge basalts (N-MORB), reflecting similar crystallization conditions and host lava composition to N-MORB. Their compositional range is relatively narrow, with Cr/(Cr + Al + Fe 3+ ) (Cr#) and Mg/(Mg + Fe 2+ ) (Mg#) varying from 0.38 to 0.48 and 0.56 to 0.72, respectively; like Cr-spinels from N-MORB, they contain low amounts of TiO 2 (0.37%-1.05%) and Fe 3+ /(Cr + Al + Fe 3+ ) (Fe 3+ #;

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“…Many magnetic nanocrystals show superparamagnetism in single domain particles below a certain critical size. Magnetic nanocrystals have been extensively applied in magnetic recording medium, information storage, bio-processing and magneto-optical devices 4,5 . The sulfur absorption capacity of milled zinc ferrite increases with decreasing crystallite size due to structure-reactivity relationship at high temperature.…”

Section: Introductionmentioning

confidence: 99%

Microstructural changes and effect of variation of lattice strain on positron annihilation lifetime parameters of zinc ferrite nanocomposites prepared by high enegy ball-milling

et al. 2012

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Zn-ferrite nanoparticles were synthesized at room temperature by mechanical alloying the stoichiometric (1:1 mol%) mixture of ZnO and α-Fe 2 O 3 powder under open air. Formation of both normal and inverse spinel ferrite phases was noticed after 30 minutes and 2.5 hours ball milling respectively and the content of inverse spinel phase increased with increasing milling time. The phase transformation kinetics towards formation of ferrite phases and microstructure characterization of ball milled ZnFe 2 O 4 phases was primarily investigated by X-ray powder diffraction pattern analysis. The relative phase abundances of different phases, crystallite size, r.m.s. strain, lattice parameter change etc. were estimated from the Rietveld powder structure refinement analysis of XRD data. Positron annihilation lifetime spectra of all ball milled samples were deconvoluted with three lifetime parameters and their variation with milling time duration was explained with microstructural changes and formation of different phases with increase of milling time duration.

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An internally consistent model for the thermodynamic properties of Fe?Mg-titanomagnetite-aluminate spinels

Cited by 211 publications

References 108 publications

Subsolidus Evolution of the Magnetite-Spinel-UlvöSpinel Solid Solutions in the Kovdor Phoscorite-Carbonatite Complex, NW Russia

Subsolidus Evolution of the Magnetite-Spinel-UlvöSpinel Solid Solutions in the Kovdor Phoscorite-Carbonatite Complex, NW Russia

Cr-Spinel in Depleted Basalts from the Lau Backarc Basin: Petrogenetic History from Mg-Fe Crystal-Liquid Exchange

Microstructural changes and effect of variation of lattice strain on positron annihilation lifetime parameters of zinc ferrite nanocomposites prepared by high enegy ball-milling

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